2012 World Junior Championships in Athletics – Men's 4 × 100 metres relay

The men's 4 × 100 metres relay at the 2012 World Junior Championships in Athletics was held at the Estadi Olímpic Lluís Companys on 13 and 14 July.

Records
, the existing world junior and championship records were as follows.

Heats
Qualification: First 2 of each heat (Q) plus the 2 fastest times (q) qualified

Participation
According to an unofficial count, 93 athletes from 22 countries participated in the event. • 🇦🇺 australia (4)

• undefined (5)

• 🇧🇭 bahrain (4)

• 🇧🇷 brazil (4)

• 🇨🇦 canada (4)

• 🇨🇿 czech republic (4)

• undefined (4)

• 🇫🇮 finland (4)

• 🇫🇷 france (4)

• 🇩🇪 germany (4)

• 🇮🇹 italy (4)

• 🇯🇲 jamaica (5)

• 🇯🇵 japan (4)

• undefined (4)

• 🇵🇱 poland (4)

• undefined (4)

• 🇪🇸 spain (4)

• undefined (4)

• 🇹🇭 thailand (4)

• undefined (4)

• undefined (5)

• 🇺🇸 united states (6)